The invention relates to a method for speech recognition in a motor vehicle. On the basis of a voice input by a user, a vehicle-internal speech recognition unit, which is referred to as an onboard speech recognition unit in this case, is used to ascertain a spoken text from the voice input. The invention also includes an infotainment system for a motor vehicle, and a motor vehicle having a processing device for performing speech recognition.
Today's infotainment systems in vehicles use systems for automatic speech recognition or ASR in order to accept voice inputs from the drivers. These ASRs may be situated either in the vehicle itself (onboard) or on remote servers (online). The recognition apparatuses can be equipped to carry out various sets of tasks.
EP 1 408 304 A1 describes a control system for a motor vehicle that allows voice control of appliances in the motor vehicle. The recognition of individual voice inputs, that is to say the conversion thereof into a machine-processable spoken text, involves the use of a vehicle-external speech recognition unit, which is referred to as an offboard speech recognition unit within the context of this document. In this regard, the related art reveals the known practice of capturing the voice sound as a voice signal, which is then digitized and is conditioned for speech recognition by feature extraction. The extracted features are then transmitted by mobile radio to the offboard speech recognition unit, which then provides its recognition result for the motor vehicle again by mobile radio. A drawback of this solution is that there must always be a mobile radio link available in order for the speech recognition to work.
EP 1 341 363 B1 describes a driver information system that likewise uses an offboard speech recognition unit. In addition, an onboard speech recognition unit can be used for simple recognition tasks, such as recognition of single control commands. In this case, a decision unit changes between the onboard speech recognition unit to the offboard speech recognition unit when required in order to convert single voice inputs by the user into a spoken text. The offboard speech recognition unit is designed only for recognition within the context of a voice dialog in this case. By contrast, the onboard speech recognition unit understands only single command words. The advantage of a voice dialog system is that a speech recognition unit can make a query if it has not understood a particular voice input. However, a drawback of this is that this results in the driver being distracted when using the speech recognition system during a journey.